Broadly speaking, coverlays are known as barrier films for protecting electronic materials, e.g., for protecting flexible printed circuit boards, electronic components, leadframes of integrated circuit packages and the like. A need exists however, for coverlays to be increasingly thin and low in cost, while not only having acceptable electrical properties (e.g., dielectric strength), but also having acceptable structural and optical properties to provide security against unwanted visual inspection and tampering of the electronic components protected by the coverlay.